1. Field of the Invention
The present invention relates to a valve assembly which is attached to a gas cylinder containing compressed gas or liquefied gas and is used for taking the gas out of the gas cylinder and charging it thereto. More specifically, it concerns a valve assembly with pressure reducing function, which makes it possible to take out high pressure gas within a gas cylinder as it is reduced to a desired low pressure when taking it out of the gas cylinder.
2. Explanation of Related Art
A conventional example of the valve assembly with pressure reducing function of this type is disclosed in U.S. Pat. No. 2,821,699 proposed earlier by an Assignee of the present invention.
The conventional valve assembly comprises a housing within which a gas inlet, a shut of f valve, a pressure reducing valve, a first check valve for retaining residual pressure and a gas outlet are arranged in series in the mentioned order. There is provided a bypass passage in parallel with the pressure reducing valve between an outlet of the shut off valve and the first check valve. The bypass passage is provided with a second check valve which inhibits a flow from the outlet of the shut off valve to the gas outlet. The pressure reducing valve has a piston which moves for opening and closing by a balance between a spring force for valve opening and a downstream pressure for valve closing.
The conventional valve assembly is excellent in that it can take out gas within a gas cylinder as its pressure is reduced by the pressure reducing valve when taking it out of the gas cylinder and besides in that it charges gas into a gas cylinder within a short period of time since it can charge the charging gas supplied to the gas outlet during the gas charging, into the gas cylinder via the bypass passage having a small flow resistance and a gap produced when the shut off valve opens. However, the conventional technique still has to be improved on the following points.
In the case where gas to be taken out must have its pressure largely reduced in comparison with that of high pressure gas within a gas cylinder, it is required to increase a pressure receiving area of the piston of the pressure reducing valve so as to smoothly move the piston for valve closing. In consequence, the conventional technique enlarges a diameter of the piston to entail a problem of making the valve assembly large and very heavy.
Further, when charging gas, the shut off valve has to be opened. Therefore, it takes labor to effect the opening operation. Also on this point, the conventional technique must be improved.
The present invention has an object to provide a valve assembly with pressure reducing function which is compact and facilitates the charging work.
In order to accomplish the foregoing object, the present invention has constructed a valve assembly in the following manner, for example, as shown in FIGS. 1 to 4, FIG. 5 or FIGS. 6 and 7.
Within a housing 3, a communication is provided between an inlet passage 11 and a shut off valve 12 and an outlet passage 13 and a gas outlet 5 in the mentioned order. Further, a bypass passage 14 and a charging port 6 communicates with each other within the housing 3. The inlet passage 11 and the bypass passage 14 communicate with an interior space (A) of a gas cylinder 1. A first pressure reducing valve 21, a second pressure reducing valve 22 and a first check valve 31 for retaining residual pressure are arranged in the outlet passage 13 in series in the mentioned order from the shut off valve 12 toward the gas outlet 5. The bypass passage 14 is provided with a second check valve 32 which inhibits a flow from the interior space (A) of the gas cylinder 1 to the charging port 6.
The present invention functions in the following manner, for example, as shown in FIGS. 1 to 4.
When taking out gas, the shut-off valve 12 is opened. Then high pressure gas within the interior space (A) of the gas cylinder 1 is reduced to a predetermined middle pressure by the first pressure reducing valve 21 and subsequently is reduced to a desired low pressure by the second pressure reducing valve 22. Thereafter, the low pressure gas is taken out of the gas outlet 5 through the first check valve 31.
While taking out the gas, if reversely flowing gas invades the gas outlet 5 for any reason, the first check valve 31 inhibits the reverse flow to prevent an interior area of the gas cylinder 1 from being contaminated with the reversely flowing gas.
When the gas is continuously taken out until a residual pressure within the gas cylinder 1 lowers to a set pressure, a first check spring 90 automatically closes the first check valve 31. This prevents further gas take-out to retain the residual pressure within the gas cylinder 1 at the set pressure.
When charging high pressure gas into the evacuated gas cylinder 1, charging gas is supplied to the charging port 6. Then the charging gas is charged into the gas cylinder 1 through the second check valve 32 of the bypass passage 14.
Consequently, the present invention produces the following advantages.
The high pressure gas within the gas cylinder is reduced in multiple stages by a plurality of pressure reducing valves. This largely reduces a diameter of a pressure receiving member (piston, diaphragm and the like) of every pressure reducing valve when compared with a pressure reducing valve of single reduction type. This enables the plurality of pressure reducing valves to be readily installed in a redundant space within the housing, which results in preventing the projection of constituent members of these pressure reducing valves from the housing to thereby make the valve assembly compact and light. The foregoing construction could provide a compact valve assembly with pressure reducing function.
In the valve assembly, the bypass passage 14 is arranged in parallel with the shut off valve 12. In this case, when charging the high pressure gas into the evacuated gas cylinder 1, the charging gas is supplied to the charging port 6 with the shut off valve 12 kept closed. Then the charging gas is charged into the gas cylinder 1 through the second check valve 32 of the bypass passage 14. This makes it unnecessary to open the shut off valve 12 when charging the gas, differently from the conventional technique. Further, it does not take much labor to charge the gas, which results in an easy gas charging.
In the valve assembly, the bypass passage 14 communicates with an inter-space between the shut off valve 12 and the first pressure reducing valve 21 of the outlet passage 13. And a closing means (C) stops gas flow-out from the gas outlet 5. The closing means (C) is provided downstream of a position where it communicates with the bypass passage 14 of the outlet passage 13, or at the gas outlet 5. In this case, after the closing means (C) has been closed, the shut off valve 12 is opened to supply the charging gas to the charging port 6. Additionally, in the event that the second check valve 32 arranged in the bypass passage 14 has lost its checking function for any reason, the shut off valve 12 is closed. Then it is possible to prevent the gas within the gas cylinder 1 from being charged from the bypass passage 14 to an exterior area through the gas charging port 6. As a result, even with the high pressure gas stored within the gas cylinder 1, the second check valve 32 can be readily repaired or replaced.
The closing means (C) can be formed from at least one of the first pressure reducing valve 21 and the second pressure reducing valve 22, for example, by making it have a set pressure on its downstream adjustable to xe2x80x980xe2x80x99 (zero). Alternatively, the closing means (C) may be composed of a second shut off valve which is arranged at a halfway portion of the outlet passage 13. In addition, the closing means (C) may be provided in a connector which is detachably attached to the gas outlet 5.
In the valve assembly, the first pressure reducing valve 21 is formed into a piston-type structure and the second pressure reducing valve 22 is constructed into a diaphragm-type structure. In this case, the first pressure reducing valve of the piston-type strongly reduces the pressure of the gas and thereafter the second pressure reducing valve reduces it with high accuracy. This can supply desired low pressure gas stably. It is a matter of course that the first pressure reducing valve of the piston-type and the second pressure reducing valve of the diaphragm-type can be formed into various structures, respectively.
In the valve assembly, a first handle 56 which opens and closes the shut off valve 12 and a second handle 82 which adjusts a set pressure of the second pressure reducing valve 22 are arranged side by side on an upper surface of the housing 3 in a horizontal direction. Further, a first pressure gauge 41 which communicates with the interior space (A) of the gas cylinder 1 and a second pressure gauge 42 which communicates with a downstream side of the second pressure reducing valve 22 are disposed side by side on a front surface of the housing 3 in a vertical direction. Moreover, the gas outlet 5 and the charging port 6 are positioned side by side in the vertical direction on any one of a rear surface and both side surfaces of the housing 3. In this case, the first and the second two handles can be operated from the same upper direction and besides the first and the second two pressure gauges can be confirmed with eyes from the same front direction. Further, a gas take-out mouthpiece and a gas charging mouthpiece can be connected to the two connection ports of the gas outlet and the charging port from the same direction, respectively. This enormously improves the operability and workability of the valve assembly. In addition, two mutually relating ones of the constituent instruments of the valve assembly are provided in the same direction. This facilitates the working of bores and threads for attaching these instruments to result in the possibility of manufacturing the valve assembly inexpensively.
In the valve assembly, when the gas outlet 5 is arranged upwards of the charging port 6 and the second pressure gauge 42 is disposed upwards of the first pressure gauge 41, it is possible to arrange at relatively high positions the gas outlet which is connected at a site where the gas cylinder is installed as well as the second pressure gauge which indicates a pressure of the gas to be taken out. This improves the working efficiency at the installation site.
In the valve assembly, if there is provided an orifice or the like flow resistance applying means 104 between the first check valve 31 and the gas outlet 5, it is possible to apply a predetermined flow resistance to gas having its pressure reduced to a desired low pressure by the second pressure reducing valve. This can control the flow amount of the gas to be taken out of the gas outlet substantially at a predetermined value.